/Engine/Source/Runtime/Engine/Public/AnimationUtils.h
The track height is defined as the minimal number of bones away from an end effector (end effectors are 0, their parents are 1, etc...)
static void CalculateTrackHeights ( const [FCompressibleAnimData](API\Runtime\Engine\Animation\FCompressibleAnimData) & CompressibleAnimData, int NumTracks, [TArray](API\Runtime\Core\Containers\TArray)< int32 > & TrackHeights )